He explained that lab animals with ulcerative colitis, and in humans with IBS, treatment with B. infantis 35624 reverses severe inflammation of the colon "and restores the immune balance from a pro-inflammatory state to an anti-inflammatory state."

To determine the impact of the probiotic on bowel movement frequency, Dr. Quigley, from University Cork College in Ireland, and colleagues randomly assigned 85 female patients with IBS to treatment with B. infantis 35624 for 4 weeks and 80 to treatment with an inert placebo.

For patients with very frequent or very few bowel movements, the bacteria had a significant effect in normalizing the frequency, the investigators reported this week at the annual meeting of the American College of Gastroenterology in Honolulu.

This is "a unique finding," Quigley noted, since "the other agents used or tested in IBS have tended to have efficacy in either a diarrhea-predominant group or a constipation-predominant group, but not in both."

Changes in bowel frequency were accompanied by "very significant improvement in individual symptoms, such as pain and bloating," he added.

"If we continue to show true efficacy for probiotics," the researcher maintained, "this will represent a major step forward because they have the great advantage of having no safety issues to confront."